Typically, a Radio Frequency (RF) receiver used in a wireless communication system can be divided into a receiver which uses a direct conversion method and a receiver which uses a heterodyne method. The direct conversion method indicates a method for directly converting a low frequency baseband signal and a high frequency signal, that is, an RF signal, and the heterodyne method indicates a method for going through an intermediate step which converts to an Intermediate Frequency (IF) and then converting and processing to an intended frequency band signal without directly converting a baseband signal and an RF signal.
The direct conversion method, compared with the heterodyne method, does not require a part for performing the IF conversion and includes a plurality of gain stages at an analog baseband stage. As a receiver using the direct conversion method includes the plurality of the gain stages, a great Direct Current (DC) offset can generate in proportion to a gain. However, as the DC offset increases, a performance of the receiver lowers. In a severe case, it can be difficult to receive a signal. Hence, it is necessary to suggest a method for calibrating the DC offset. Herein, mostly, the DC offset indicates a common mode voltage difference generated in two signal paths, that is, a DC level difference in a circuit of a differential structure having the two signal paths.
To cancel the DC offset, the related art used a method for cutting off low frequencies using a high pass filter or a low pass filter. However, such a method has a disadvantage of causing signal attenuation according to a modulation method or a cutoff frequency of the pass filter and thus degrading the performance of the receiver.